1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane

Endpoint summary

Description of key information

For skin irritation, there are two in vitro skin irritation studies (Eurofins, 2022a and b, reliability 1) using reconstituted three-dimensional human epidermis models conducted according to OECD Test Guideline 439 and in compliance with GLP. These tests are used as a replacement for the Draize Skin Irritation Test (OECD TG 404) to distinguish between UN GHS Category 2 skin irritating test substances and not categorised test substances. 1,1,1,5,5,5-Hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3, EC 222-613-4) was categorised as a non-irritant using both the EPIDERM™ and EPISKIN-SM™ tissue models.

There are no in vivo skin irritation data available for the registered substance.

For eye irritation, there is an in vitro Bovine Corneal Opacity and Permeability (BCOP) study available for 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3, EC No. 222-613-4) conducted according to Test Guideline 437 and according to GLP (Bioservice Scientific Laboratories, 2022, reliability 1). In this study, the test item did not induce ocular irritation through either endpoint and resulted in a mean in vitro irritancy score (IVIS) of 0.30 after 10 ± 1 minutes of treatment. Since the IVIS was ≤ 3, the test item is classified into UN GHS 'No Category'.

Supporting data are available for a structural analogue which are included to support read-across for the skin sensitisation. A study for eye irritation was read-across from 1,1,1,3,5,5,5-heptamethyl-3-trimethylsilyl)oxy]trisiloxane and reported the test material to be not irritating to the eyes of rabbits, in a study conducted to an equivalent OECD Test Guideline but not compliant with GLP (Haruna, 2001, reliability 2).

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Reference 1

Endpoint:

skin irritation: in vitro / ex vivo

Remarks:

EPISKIN-SM™

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Dec 2021 to 29 March 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

2021/EPISKIN-Standard Model™

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Remarks:

reconstituted three-dimensional human skin model EPISKIN-SM

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: Not specified

Source strain:

other: Not applicable

Details on animal used as source of test system:

Not applicable

Justification for test system used:

This test uses the EPISKIN-Standard Model™ (EPISKIN-SM™), a reconstructed human epidermis model (EpiSkin) which consists of normal human epidermal keratinocytes (NHEK) and, therefore, represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human skin, i.e., the epidermis. The EPISKIN-Standard Model™ (EPISKIN-SMTM) was used as a replacement for the Draize Skin Irritation Test (OECD TG 404) to distinguish between UN GHS “Category 2” skin irritating test substances and not categorized test substances (“No Category”) which may be considered as non-irritant.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN-SM™
- Tissue batch number(s): 22 EKIN 009
- Production date: not specified
- Shipping date: not specified
- Delivery date: not specified
- Date of initiation of testing: 02 February 2022

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: Room tremperature
- Temperature of post-treatment incubation (if applicable): 37±1 °C,

REMOVAL OF TEST MATERIAL AND CONTROLS
- Number of washing steps: The tissues were washed with DPBS to remove any residual test item. Excess DPBS was removed by blotting bottom with blotting paper.
- Observable damage in the tissue due to washing: None reported
- Modifications to validated SOP: None

DYE BINDING METHOD
- Dye used in the dye-binding assay: MTT
- Incubation time: 3 hours ±5 min
- Spectrophotometer: Plate spectrophotometer
- Wavelength: OD was measured at 570nm
- Filter: Filter band
- Filter bandwidth: 30nm
- Linear OD range of spectrophotometer: without reference wavelength

NUMBER OF INDEPENDENT TESTING RUNS / EXPERIMENTS TO DERIVE FINAL PREDICTION: One pre-experiment and one main experiment

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- The test substance is considered to be irritant to skin if the viability after 15 minutes exposure is less than 50%
- The test substance is considered to be non-irritant to skin if the viability after 15 minutes exposure is greater than or equal to 50%
- Justification for the selection of the cut-off point(s) if different than recommended in TG 431 and 439: not applicable

Control samples:

yes, concurrent negative control

yes, concurrent no treatment

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 μL (26.3 μL/cm2)
- Concentration (if solution): Undiluted (neat)

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL
- Concentration (if solution): Dulbecco's Phosphate Buffering Saline (DPBS)

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL
- Concentration (if solution): 5% sodium dodecyl sulfate (SDS)

Duration of treatment / exposure:

15 minutes

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

Three

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Experiment 1

Value:

> 50

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: No
- Direct-MTT reduction: The test item showed no non-specific MTT reducing potential, therefore no additional controls for correction of results were necessary.
- Colour interference with MTT: The test item showed no colouring potential, therefore no additional controls for correction of results were necessary.

DEMONSTRATION OF TECHNICAL PROFICIENCY:
- Mean OD570 nm six blank values: 0.046; cut off < 0.1;
- Mean Absolute OD570 nm negative control: 0.797, cut off ≥ 0.6 and ≤1.5;
- Mean Relative Viability [% negative control] of the positive control: 12.5; cut off < 40%;
- Max. SD Viability of replicate tested tissues of all dose groups [%]: 10.8, cut off ≤ 18%

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes
- Range of historical values if different from the ones specified in the test guideline: not applicable

Interpretation of results:

GHS criteria not met

Conclusions:

In the in vitro skin irritation study with 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3) conducted according to OECD 439 and in compliance with GLP using the EPISKIN-SM™ tissue model, the reported mean relative tissue viability (% negative control) was >50% (106.7%) after 15 minutes treatment and 42 hours post-incubation. The positive control produced the expected reduction in viability. The test item is therefore categorised as a 'non-irritant' ('No Category') as applicable under the CLP and UN GHS and under the conditions and limitations of the model.

Reference 2

Endpoint:

skin irritation: in vitro / ex vivo

Remarks:

EpiDerm™

Type of information:

experimental study

Adequacy of study:

key study

Study period:

02 Dec 2021 to 28 Jan 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

2021/EpiDerm™-Standard Model (EPI-200™)

Deviations:

yes

Remarks:

Updated MatTek protocol (Version 12-Apr-2020)

GLP compliance:

yes (incl. QA statement)

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: not specified

Source strain:

other: not applicable

Details on animal used as source of test system:

Not applicable

Justification for test system used:

This test uses the EpiDerm™ reconstructed human epidermis model (MatTek) which consists of normal human epidermal keratinocytes (NHEK) and, therefore, represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human skin, i.e., the epidermis.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDermTM /MatTeK
- Tissue batch number(s): 36119
- Production date: not specified
- Shipping date: not specified
- Delivery date: not specified
- Date of initiation of testing: 25 January 2022

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: Plates were incubated for 25 ± 1 min under sterile flow at room temperature and then 35 ± 1 min at 37°C.
- Temperature of post-treatment incubation (if applicable): 37 ± 1 °C
REMOVAL OF TEST MATERIAL AND CONTROLS
- Number of washing steps: Tissues were washed by filling and emptying the inserts 15 times with DPBS using a constant stream in about 1.5 cm distance from the tissue surface, this process also occurred sequentially, e.g., in one-minute intervals. Subsequently, the inserts were completely submerged three times in 150 mL DPBS and shaken to remove remains of the test item. Finally, the inserts were rinsed once from the inside and the outside with sterile DPBS. Excess DPBS was removed by blotting the bottom with blotting paper.
- Observable damage in the tissue due to washing: None reported
- Modifications to validated SOP: Updated protocol version Apr 2020

DYE BINDING METHOD
- Dye used in the dye-binding assay: MTT
- Spectrophotometer: plate spectrophotometer
- Wavelength: 570 nm
- Filter: Filter band
- Filter bandwidth: ± 30 nm

NUMBER OF INDEPENDENT TESTING RUNS / EXPERIMENTS TO DERIVE FINAL PREDICTION: one

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- No irritant effects when the mean relative tissue viability (% negative control) is > 50% after 60 min treatment and 42 h post-incubation.
- Justification for the selection of the cut-off point(s) if different than recommended in TG 429: Not applicable

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied: 30 μL
- Concentration (if solution): 47 μL/cm2 (undiluted)

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 μL Dulbecco’s phosphate buffered saline (DPBS)
- Concentration (if solution): N/A

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 μL sodium dodecyl sulfate (SDS)
- Concentration (if solution): 5%

Duration of treatment / exposure:

1 hour

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

Three per dose group

Irritation / corrosion parameter:

% tissue viability

Value:

> 50

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: None
- Direct-MTT reduction: The mixture of 30 μL test item per 1 mL MTT medium showed no reduction of MTT compared to the solvent. The mixture did not turn blue/purple. Therefore, NSMTT equalled 0%.
- Colour interference with MTT: The mixture of 30 μL of the test item per 300 μl aqua dest. and/or per 300 μL isopropanol showed no colouring detectable by unaided eye-assessment. Therefore, NSC equaled 0%.

DEMONSTRATION OF TECHNICAL PROFICIENCY: Yes

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: mean absolute OD570 nm of the three negative control tissues is ≥ 0.8 and ≤ 2.8
- Acceptance criteria met for positive control: mean relative tissue viability of the three positive control tissues is < 20%
- Acceptance criteria met for variability between replicate measurements: standard deviation (SD) of relative tissue viability obtained from each three concurrently tested tissues is ≤ 18%.
- Range of historical values if different from the ones specified in the test guideline: See Table 4 in attached background material. Historical data were generated from 2015 to 2021.

Interpretation of results:

GHS criteria not met

Conclusions:

In the in vitro skin irritation study with 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3) conducted according to OECD 439 and in compliance with GLP using the EPIDERM-SM™ tissue model, the reported mean relative tissue viability (% negative control) was >50% (99.2%) after 60 minutes treatment and 42 hours post-incubation. The positive control produced the expected reduction in viability. The test item is therefore categorised as a 'non-irritant' ('No Category') as applicable under the CLP and UN GHS and under the conditions and limitations of the model.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 March 2022 to 13 April 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)

Deviations:

yes

Remarks:

Due to a delay in delivery, the medium (Hanks' balanced salt solution with Ca++ and Mg++ and containing penicillin/streptomycin) used for transport was not available. Therefore, it was substituted with RPMI 1640 (without phenol red) containing Pen/Strep.

GLP compliance:

yes (incl. QA statement)

Species:

cattle

Strain:

not specified

Details on test animals or tissues and environmental conditions:

TEST TISSUE:
- Source: Fresh eyes were collected from the slaughterhouse and were transported in RPMI 1640 medium (without phenol red) containing 1% Pen/Strep on ice to the laboratories. Immediately after arrival of the eyes, cornea preparation was initiated.

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 750 µl
- Concentration (if solution): undiluted

Duration of treatment / exposure:

10 minutes incubation with the test substance at 32 ± 1 ºC

Observation period (in vivo):

Not applicable

Number of animals or in vitro replicates:

Three corneas were used for the test substance, positive controls and negative controls

Details on study design:

NUMBER OF REPLICATES : Three

NEGATIVE CONTROL USED : 0.9% physiological saline

SOLVENT CONTROL USED: not applicable

POSITIVE CONTROL USED : 100% ethanol

APPLICATION DOSE AND EXPOSURE TIME : 750 µl for 10 minutes exposure time at 32 ± 1 °C

TREATMENT METHOD: The assay uses isolated corneas obtained as a by-product from animals freshly slaughtered at the abattoir Vion Beef B.V., Buchloe, Germany. On the test day, fresh eyes were collected from the slaughterhouse and were transported in RPMI 1640 medium (without phenol red) containing 1% Pen/Strep on ice to the laboratories. Immediately after arrival of the eyes, cornea preparation was initiated. The eyes were carefully examined for defects and any defective eyes were discarded.
The tissue surrounding the eyeball was carefully pulled away and the cornea was excised leaving a 2 to 3 mm rim of sclera. The isolated corneas were stored in a petri dish containing RPMI 1640 medium. Before the corneas were mounted in corneal holders (Duratec GmbH) with the endothelial side against the O-ring of the posterior chamber, they had been visually examined for defects and any defective cornea had been discarded. The anterior chamber was then positioned on top of the cornea and tightened with screws. The chambers of the corneal holder were then filled with RPMI 1640 medium (without phenol red) containing 1% FBS and 2 mM L-glutamine (complete RPMI 1640 medium). The posterior chamber was always filled first. The corneas were incubated for one hour at 32 ± 1 °C.

POST-INCUBATION PERIOD: After the equilibration period, the medium was removed from both chambers and replaced with fresh complete RPMI 1640 medium. An initial measurement was performed on each of the corneas using the opacitometer. Three corneas with illuminance readings approximately equivalent to the median illuminance of all corneas were selected as negative-control corneas. The illuminance of each cornea was read and recorded. Only corneas that had an initial illuminance reading I > I₀/1.1651 lux were used for the assay. The medium was removed from the anterior chamber and replaced with the test item or control. 750 µl Of the test substance or the control substance was introduced into the anterior chamber. After 10 minutes incubation at 32 ± 1 °C either the test substance or the control substance was removed and the epithelium washed at least three times with MEM (containing phenol red).

REMOVAL OF TEST SUBSTANCE :
- Number of washing steps after exposure period: One
- POST-EXPOSURE INCUBATION: Once the medium was free of test substance, the cornea was finally rinsed with complete RPMI 1640 medium (without phenol red). The anterior chamber was refilled with complete RPMI 1640 medium and an illuminance measurement was performed after 2 hours incubation at 32 ± 1 °C. Inadvertently, after final rinse with complete RPMI 1640 medium and subsequent aspiration, the chambers of cornea no. 9 (test item group) were refilled with medium not before but after post-incubation, shortly before the illuminance measurement was performed.

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity: The following formula was used to calculate the opacity:
Opacity= Opacity= ((I₀/I ) - b)/a
where a = 0.025 and b = 0.9894 (values a and b are equipment specific variables empirically determined by the manufacturer).
The value I₀ is the illuminance through a holder without cornea, but with windows and liquid. This value is determined by taking the mean for a set of cornea holders and is re-evaluated periodically.
The change in opacity for each cornea was calculated by subtracting the initial opacity reading from the final opacity reading. These values were corrected by subtracting from each the average change in opacity observed for the negative-control corneas. The mean opacity value for each treatment was calculated by averaging the corrected opacity values of each cornea for a given treatment.

- Corneal permeability: The passage of sodium fluorescein dye measured with the aid of Jenway 6405 UV/VIS spectrophotometry (OD490). The OD490 value of a blank cuvette containing medium without fluorescein is measured before setting the spectrophotometer to zero. The blank value is subtracted automatically at each measurement. All measurements were in the linear range of the spectrophotometer (OD490 should be less than 1.500). The final-corrected OD490 of the test article and the positive control were calculated by subtracting the corrected OD490 of the negative-control corneas from the corrected OD490 value of each treated cornea:
Final-corrected OD490 = (OD490 – blank OD490) – average of blank-corrected negative control OD490
The mean OD490 value of each treatment group was calculated by averaging the final corrected OD490 values of the treated corneas for that treatment condition.

- Others (e.g, pertinent visual observations, histopathology): Each cornea was observed visually and pertinent observations were recorded.

SCORING SYSTEM: In Vitro Irritancy Score (IVIS) calculated using the following formula: IVIS = mean opacity value + (15 x mean permeability OD490 value)

DECISION CRITERIA: Appropriate decision criteria for Test Guideline 437 were used. The IVIS cut-off values for identifying the test items as inducing serious eye damage (UN GHS Category 1) and test items not requiring classification for eye irritation or serious eye damage (UN GHS No Category) are:

In vitro irritancy score ≤ 3 has a UN GHS 'No Category',
In vitro irritancy score range > 3; ≤ 55 UN GHS 'No prediction can be made',
In vitro irritancy score >55 has a UN GHS 'Category 1'.

Irritation parameter:

in vitro irritation score

Run / experiment:

Mean value

Value:

0.3

Vehicle controls validity:

not examined

Negative controls validity:

valid

Remarks:

The negative control responses resulted in opacity and permeability values that are less than the established upper limits for background bovine corneas treated with the respective negative control (opacity 2.23; permeability 0.065).

Positive controls validity:

valid

Remarks:

The in vitro irritation score obtained with the positive control fell within the two standard deviations of the current historical mean and therefore this assay is considered to be valid.

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

OTHER EFFECTS:
- Visible damage on test system: None observed

DEMONSTRATION OF TECHNICAL PROFICIENCY: Yes

ACCEPTANCE OF RESULTS: The test conditions were adequate and the test system functioned properly.
- Acceptance criteria met for negative control: The negative control responses resulted in opacity and permeability values that are less than the established upper limits for background bovine corneas treated with the respective negative control (opacity 2.23; permeability 0.065).
- Acceptance criteria met for positive control: The in vitro irritation score obtained with the positive control fell within the two standard deviations of the current historical mean and therefore this assay is considered to be valid.
- Range of historical values if different from the ones specified in the test guideline: See attached results Table 4

See attached background material for results tables.

Interpretation of results:

GHS criteria not met

Conclusions:

In the Bovine Corneal Opacity and Permeability (BCOP) Study conducted according to OECD Test Guideline 437 and in compliance with GLP, the test item did not induce ocular irritation through either endpoint and resulted in a mean in vitro irritancy score (IVIS) of 0.30 after 10 ± 1 minutes of treatment. Since the IVIS was ≤ 3, the test item is classified into UN GHS 'No Category'.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

In the first of two key in vitro skin irritation studies with 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3, EC 222-613-4) conducted according to OECD Test Guideline 439 and in compliance with GLP, the EPISKIN-SM™ tissue model was used as a replacement for the Draize Skin Irritation Test (OECD TG 404). The test item had no non-specific MTT-reducing or colouring potential, therefore, no additional controls were necessary. The reported mean relative tissue viability (% negative control) was >50% (106.7%) after 15 minutes treatment and 42 hours post-incubation. According to the criteria upon which the interpretation is based, the result is negative for skin irritation and the registered substance was therefore categorized in this model as a 'non-irritant' ('No Category') as applicable under the CLP and UN GHS and under the conditions and limitations of the model. The mean absolute OD570 nm of the three negative control tissues was ≥0.6 and ≤1.5 (0.797). The mean relative tissue viability (% negative control) of the three positive control tissues was <40% (12.5%) and the maximum standard deviation of viability of replicate tissues of all dose groups was <18% (10.8%). The controls confirm the validity of the study (Eurofins, 2022a, reliability 1).

A second in vitro study assessing skin irritation was also carried out to confirm the validity of the irritation outcome of the first study using the EpiSkin method. In the second key in vitro skin irritation study with 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3, EC 222-613-4) conducted according to OECD Test Guideline 439 and in compliance with GLP, the EPIDERM™ tissue model was used as a replacement for the Draize Skin Irritation Test (OECD TG 404). The test item had no non-specific MTT-reducing or colouring potential, therefore, no additional controls were necessary. The reported mean relative tissue viability (% negative control) for was > 50% (99.2%) after 60 minutes of treatment and 42 hours post-incubation. According to the criteria upon which the interpretation is based, the result is negative for skin irritation and the registered substance was therefore categorized in this model as a 'non-irritant' ('No Category') as applicable under the CLP and UN GHS and under the conditions and limitations of the model. The mean absolute OD570 nm of the three negative control tissues was ≥ 0.8 and ≤ 2.8 (1.783). The mean relative tissue viability (% negative control) of the three positive control tissues was < 20% (4.5%) and the maximum standard deviation of viability of replicate tissues of all dose groups was <18% (13.2%). The controls confirm the validity of the study (Eurofins, 2022b, reliability 1).

In the supporting in vivo read-across study for skin irritation, test animals were administered 50% or 90% solution of test material in olive oil onto intact or abraded skin (Haruna, 2001b, reliability 2). No signs of irritation were observed in any of the animals at either dose, at any observation time points of 1, 24, 48 and 72 hours after removal of the patches. No clinical signs were observed in any animals throughout the observation period. The body weights of all animals increased satisfactorily throughout the observation period. The study was conducted according to a Japanese protocol similar to OECD Test Guideline, but not in compliance with GLP.

The eye irritancy potential of 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3) was investigated in the bovine corneal opacity and permeability assay (Bioservice Scientific Laboratories, 2022, reliability 1). All 3 corneas treated with the test substance showed spots with slight opacity of the tissue. The in vitro irritation score obtained with the positive control fell within the two standard deviations of the current historical mean and therefore the assay was considered to be valid. The negative control responses resulted in opacity and permeability values that were less than the established upper limits for background bovine corneas treated with the respective negative control. The mean in vitro irritation score (IVIS) was 0.30 and since the IVIS was ≤ 3, the test item was classified into UN GHS 'No category'.         

In the supporting read-across study for eye irritation, test animals received a single instillation of 50% or 90% solution of test material in olive oil into the eye (Haruna 2001d, reliability 2). No eye irritation was observed in the cornea, iris or conjunctivae of the 3 animals at any observation time point in response to 50% or 90% solution, or in response to vehicle control of olive oil, applied to the other eye of the animals. No clinical signs were observed in any animals throughout the observation period and the body weights of all animals increased satisfactorily throughout the observation period.

Justification for classification or non-classification

Based on the available data, 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane does not require classification for skin or eye irritation in accordance with current Regulation (EC) No 1272/2008.